Sereia Thalassa Selene, a siren trained to believe the royal Valmontt bloodline is the root of centuries of war, infiltrates the human kingdom of Aurelune by posing as a foreign princess during a grand royal celebration. Her mission is simple: get close to Crown Prince Alden and kill him to weaken the throne and end the cycle of conflict between their peoples. But inside the palace, nothing goes as planned—especially when Prince Alden begins to notice that his mysterious guest may not be who she claims to be, and Sereia finds herself caught between her mission, her lies, and a world that is far more complicated than she was ever taught.